Although with the cloning of the cDNA for the amyloid precursor protein (APP) in late 1986 the sequences and identification of APP have been possible, the importance of APP in the pathogenesis of Alzheimer Disease (AD) is essentially unknown. During the previous funding period, several immunochemical and biochemical probes were produced and used by this laboratory to conclude that neurons are the major source of APP in the senile plaque, the site of the amyloid deposition. They suggest these findings are directly relevant to their original hypothesis: that the intraneuronal cytoskeletal changes of AD, neurofibrillary pathology (NFP), is a direct result of the interaction of APP with the cytoskelton. The finding that NFP contains abundant heparin sulfate proteoglycans (HSPG) gave them a chemical basis for this binding, since APP is an ASPG binding protein. In binding studies, they found that many NFP components specifically associate with APP accumulations. Support was therefore found for the hypothesis that NFP components are incorporated through reciprocal binding. In the present proposal, they will extend these studies through the following aims: (1) Binding studies that will define NFP's biochemistry in situ as well as traditional biochemical properties; (2) determine whether HSPG's are associated with the NFP's of other diseases; (3) determine the relationship of neuritic change to amyloid deposition in AD and control brains; (4) study the effect of APP gradients in the brain through brain implants of APP and B-protein; (5) physical mapping of NFP epitopes.